Grinding machine



H. E. KEMPTON El' AL GRINDING MACHINE Filed Feb. 4, 1925 '7 sheets-sheet 1 I l l I u l l l L, fll

Oct. 15, 1929.

Oct. 15, 1929. H. E. KEMPToN ET AL 1,731,719

GRINDING MACHINE Filed Feb. 4, 1925 IIIIIIIII IIII |||II|| I |||I| Oct. l5, 1929. H. E. KEMPTON Er A1.

GRINDING MACHINE 7 Sheets-Sheet 3 i i A Filed Feb. 4, 1925 Oct. 15, 1929. H. E. KEMPTON Er AL GRINDING MACHINE Filed Feb. 4, 1925 '7 Sheets-Sheet 4 www @QH Qmw QE. Qu @QH NNN NN mw.

Oct 15, 1929. H. E. KEMPTQN n M. 1,731,719

GRINDING MACHINE Filed Feb. 4, 1925 '7 sheets-sheet 5 lllllllfI/ll,

GRINDING- MACHINE Filed Feb. 4, 1925 '7 Sheets-Sheet 6 '7 Sheets-Sheet 7 f Joa Oct. 15, 1929. H. E. KEMPTN Er AL GRINDING MACHINE Filed Feb. 4, 1925 grinding wheel before thel Parental oa. 1s, l1929 UNITED STATES PATENT OFFICE HERBERT E. KEMPTON .AND KEITH F. GALLIMOBE, F FOND DU LAC, WISCONSIN,

ASSIGNORS, BY MESNE ASSIGNMENTS,

T0 THE HEALD MACHINE COMPANY, Ol'

WORCESTER, MASSACHUSETTS, A CORPORATION 0F MASSACHUSETTS @BINDING MACHINE Application filed February 4, 1925. Serial No. 6,689.

This invention relates to improvements in grinding machines, and is herein shown as embodied in an internal grinding machine of the type disclosed in U. S. Letters Patent No.

1,534,302, issued April 21, 1925, to Prentice- Conradson and ourselves. v

A general object of the invention isto provide a grinding machine with a novel automatic wheel truing device the operation of which is incidental to and controlled by the main operation of the machine. i The primary object of the invention resides in the provision, in a grinding machine, of automatic means for dressing and truing the workpiece is brought to the desired size. According to this feature of the invention, therefore, the wheel truing operation is interposed in the cycle of grinding, so that the final and finishing cuts, which bring the workpiece to the desired size, are taken with a wheel which -is not only sharp and clean cutting, but is of truly cylindrical shape. It will be seen that the foregoing has the greatest utility in a grinding machine having automatic means for causing cessation of the grinding operation, for in this manner a high production can be attained while maintaining high precision standards for the finshed workpieces.

A second important feature of the invention resides in the fact that the dressing opi eration, which takes place automatically as above mentioned, is effected by withdrawing the grinding wheel from the workpiece, moving the grinding wheel past a dressing device, and subsequently returning the wheel to the workpiece. The workpiece is brought to the finished size, according to this feature of the invention, by a wheel which maintains continuous contact with it, albeit the usual reciprocatory traverse motion between wheel and workpiece is employed. In this manner detrimental bell-mouthing of the workpiece (in the case of an internal grinding machine) or excessive grinding of the end surface of the work (in the case of grinding machines generally) is avoided.`

Still another feature of the invention resides in the employment of the carriage moving mechanism to eifect the dressing operation aforesaid. Most 'nding machines, including internal grin ing machines, are provided with a table or carriage, carrying indifferentl the grinding wheel or the workhead, an by the movement of which a reclprocatory traverse between wheel and wor iece is secured. The purpose and utility o this motion is too well known to require discussion here. We utilize this -carriage moving mechanism as aforesaid, the novelty residing in the control thereof and in the automatic increased traverse interposed in a succession of limited traverses.

A more specific object resides in the provision for grinding machines of a novel wheel truino' device which has a dressing tool adapted tolie projected into the path of the grinding wheel, and the` operation of which is automatically controlled by the progress of the grinding operation.

A further object is to provide means for slowing down the movement ofthe grinding wheel carriage while the cutting face of the grinding wheel is moving past the dressing tool in the truing operation.

A detailed object is to provide a high speed grinding machine which has a grinding .wheel carriage; which has means to automatically gage the work; which has means controlled by said gaging means for effecting relative coarse andfine cross feeds between said carriages; which' has pressure-Huidoperated means under the control of said gaging means foradvancing said grinding wheel carriage from its remote inoperative position into its operativeposition and reciprocating it in the latter position, returning said carriage part way to its inoperative position upon stopping the coarse cross feed, immediately advancing said carriage again into its operative position and reciprocating it therein, and finally returning said carriage to and stopping it in its inoperative position upon stopping the fine cross feed; and which has a wheel truing means also controlled by ,said gaging means to dress the grinding draulically operated.

A further object is vconcerned with the electrical devices and circuits by which the various parts of the machine are automatically operated in' harmony and synchronism.

Ancillary objects and advantages will' become apparent as the descriptionproceeds.

In the accompanying drawings, Figure 1 l is a front side view of a grinding machine embodying the features of our invention in its-preferred form, and of which partsv have been broken away to show the gage member. Figure 2 is a top plan View of the machine. Fig. 3 is a rear side view of the machine. Fi 4 is a .diagrammatic representation of the e ectric circuits and the hydraulic system for operating and controlling the machine parts, certain of the latter being shown in part or in section.

Fig. 5 is a fragmentary view of a modified form of dressing means adapted to be hy- Fig. 6 is a vertical section through the feed mechanism taken along line 6-6 of Fig. 2. Fig. 6" is a fragmentary side View of one of the locking means for the electromagnets of the feed mechanism. Fig. 7 is a sectional View taken along line 7--7 of Fig. 1 and showing the double switch' controlled by the gage member.

Fig. 8 is a fragmental vertical section through the control means governing the movements of the grinding wheel carriage, said section being taken substantially in the plane of line 8 8 of Fig. 1.

Fig. 9 is a sectional view of the reversing switch controlling the movement of the grinding wheel carriage.

Fig. 10 is an enlarged sectional view of the dressing mechanism shown in Fig. 2.

Fig. 11 is a perspective View of one of the reversing dogs.

Fig. 12 is a perspective view of. another do l Vhile our invention is susceptible of various modifications, alternative constructions, and adaptations, we have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that we do not thereby intend to limit ourselves to the specic form disclosed, but aim in the appended claims to cover all modiications, alternative constructions and adaptations falling within the spirit and scope of the invention.

Referring now more particularly to the specific construction of the exemplary embodiment of the invention, the, machine comprises a hollow base casting 10 having an interna] transverse wall 11 which separates the base into a long bed on whichl a grinding spindle carriage 12 is mounted and a wide portion on which a headstock carriage. 13 is mounted. Between the wall 11 and another transverse wall 14 is a chamber adapted to contain a coolant fluid for the work, and between the Wall 14 and a third transverse wall 15 is a reservoir adapted to contain a pressure fluid,

such as oil, for actuating the carriages 12 and 13.

The grinding spindle carriage The carriage 12 is arranged to be recipro-' cated by a piston and cylinder unit, one element of which is mounted on the carriage to travel therewith. Preferably the cylinder 22 is rigidly secured to the underside of the carriage 12, and the piston 23 is stationarily supported by hollow rods 24 having their remote ends mounted in the machine base. These rods communicate with the cylinder 22 at opposite sides of the piston 23 to introduce and .permit the escape of pressure fluid.

The headstocc carriage The headstock carriage 13 comprises a body section 25 which is slidably mounted on transverse ways 26 formed -on the base 10, and a top section 27 which is rotatablymounted in the body section and extends therethrough into the base 10. J ournaled in the top section 27 is a rotary work spindle 28 which carries a suitable chuck or work fixture 29 at one end for holding the work to be ground, and which is driven through suitable connections including a change speed gearing 30 by an electric motor 31 mounted with the gearing on the underside of the top section to move or rotate therewith.

The feeding mechanism ratchet Wheel 35 (see Fig. 6) is ixed on the feed screw, and is adapted to be rotated inter- .mittently and by small degrees by means of either one of two feed pawls 36 and 37. These pawls are pivotally mounted on the oppositely extending arms of two bell-crank levers '38 and 39, respectively, loosely supported by the feed screw 32, and are drawn toward the ratchet wheel 3 5 by springs 40. The otherarms of the bell-crank levers extend in the same direction, and are provided with cams' 41 adapted to be engaged by a lever 42 to recprocate the pawls. The degree of oscillation of these arms can be independently adjusted by means of two ercentrics 43 underlying them and limiting the downward movement of the cams 41. In practice, the eccentrics 43 are so adjusted that the pawl 36, designated as the coarse feed pawl, is given a rc atively large reciprocation, and the pawl 37` designated as the fine feed pawl is given a relatively small reciprocation. The lever 42 is oscillatcd b means of la floating piston 44 reciprocable 1n a stationary cylinder' 45, the opposite ends of which alternately receive and discharge pressure fluid.

Mounted in the feed box 33 are a pair of elcctromagnets 46 and 47 provided with armatures 48 and 49 having tracks 50 and 51 'respectively. The latter underlie rollers 52 and 53 on the pawls 36 and 37, and upon excitation of the electromagnets will render the pawls inoperative.- Upon first exciting the electromagnet 46 and then the electromagnet 47, the pawls 36 and 37 will be successively rendered inoperative, thereby reducing and finally discontinuing the cross feed of the headstock carriage 13 as the grinding operation progresses. To permit manual operation of the feed screw by means of the hand wheel 34, the pawls 36 and 37, after each excitation of the electromagnets, are automatically locked in inoperative position by a pair of latches 54 engaging the heels of the armatures 48 and 49. The latches 54 are mounted on a pair of shafts l55 together with releasing levers 56 which are connected by a suitabl'e linkage and which can be oscillated simultaneously by a lever 57 to disengage the latches and thereby release the pawls.

The gag/ng mechanism i a gage rod 58 having a pair of gages 59 and 60, designated respectively as a coarse feed gage and a fine feed gage, mounted onv its forward end. These gages are adapted to gage the work being ground, such as the blank A centrally mounted in the chuck 29, and the gage 59 is slightly smaller and a little in advance ofthe gage 60 to permit the former to enter the bore of the blank sometime before the latter. The rear end of the gage rod 58 is connected by a bracket 61 to that of a parallel push rod 62 reeiprocable in the top section 27 and carrying an abutment roller 63` at its forward end. A coil spring 64 on the push rod 62 tends to move the gages forward into yielding engagement with the blank A, and an adjustable abutment 65 on the grinding spindle carriage 12 is adapted to strike the roller 63 to withdraw the gages as the grinding wheel 19 advances into the bore of the blank. The gages thus automatically and periodically attempt to enter the bore of the work. When the grinding operation nears on the machine base.

completion, the coarse feed gage 59 only will enter the bore, and when the operation is com leted both gages will enter.

ounted on the bracket 61 and extending longitudinally into a pair of insulating tubes 66 `on the top section 27 of the headstock carriage 13 are a pair of spring pressed contacts 67 and 68 (see Fig. 7) which are movable with the gage rod 58 and which are adapted to successively engage two pairs of contact pins 69 and 70, projecting into the tubes, as the gages 59 and 60 respectively enter the bore of the the electromagnet 47 to control the progress of the grinding operation in amanner already described.

T he operating mechanism Hydraulic pressure fluid, preferably oil, is drawn from the oil reservoir in the machine base 10 through a pipe 73 (see Fig. 3) by an oil pump 74 driven by an electric motor 75, said pump and said motor being mounted on the rear side of the base. The oil is discharged from the pump 74 through a pipe 76 which communicates with the inlet port 77 (see Figs. 1 and 4) of a main control valve 78 mounted on the front side of the machine. This valve is formed with ports 79 and 80 connected to the remote ends of the hollow piston rods 24 for the grinding spindle carriage 12 by pipes 81 and 82, and to opposite ends of the vcylinder 45 for the feeding mechanism by valve 78 through either of the ports 7 9 or 80 is returned through theoutlet ports 85 to the oil reservoir. The flow of oil through the valve 78 is controlled by a reciprocable valve member 86 adapted to connect the ports 79 and 80 successively and. alternately with the ports 77 and 85. When the valve member 86 is in a central or neutral position, the oil will be by-passed directly from the inlet port 77 to the outlet ports 85. The volume of the oil can be changed to vary the speed at which the carriages 12 and 13 move by means of a hand lever 87 for adjusting a change speed gearing 88 in the connection bet-Ween the motor 75 and the pump 74.

The valve member 86 is provided with a stem 89 pivotally connected to the lower end of an actuator which is in the form of an upright lever 90 pivoted between its ends at 91 Movement of the lever 90 to the right or left will reciprocate the valve member 86 to cause movement of the spindle carriage 12 toward or from the chuck29 (see Figs. 1 and 8). A pivoted dog 92 is mounted in the upper end of the lever 90, and is normally vmaintained by a spring follower 93 inoperative position 4in the path of three dogs 94, 95 and 96 (see Figs. 1 and 4) which are adjustabl vsecured to the front depending side 17 o the carriage 12 by bolts engaging in the T-slot 97. .The dogs 95 and 96 lare beveled at their .left ends, and upon movement of the carriage 12 from itsI inoperative position, shown in Fig. 1, to the left will successively engage and ldepress the pivoteddog 92 out of their way to permit the latter to snap into position between the dogs 94 and 95. Upon continued movement of the carriage 12, the dogs 94 and 95 will automatically oscillate the lever 90 to 'reciprocate the carriage. The distance through which the carriage will reciprocateA depends upon the spacing of the dogs 94 and 95, and corresponds to the length of the bore in the piece of workto be ground, the dogs being so positioned on the carriage that the grinding wheel 19 will reciprocate from one end of the bore to the other.

Means is provided for automatically tripping the pivotal dog 92 when the coarse feed gage 59 and also when the fine feed gage 60 enters the work. This means comprises 'an `electromagnet 98 (see Figs. 8 and 4) mounted in a suit-able housing 99 'secured to the base of the machine, and having a pivotal armature 100 tothe free end of which a sli dable pin V101 is attached. The pin 101 is arranged to engage the dog 92 and swing it out of the path of the dogs 95 and 96, but not far enough to be out ofthe path of the dog 94. A catch 102 mounted in the housing 99 is adapted to drop behind the pin 101 when the armature 100 is attracted by the magnet coil to hold the dog 92 in tripped position. The catch 102 is provided with a pin or projection 103 which is adapted to ride upon a cam face 104 on the dog 95 and also upon two cam faces 105 on opposite sides of a dog 106 mounted on the .left end of the carriage 12, and which is 'thereby adapted to release the pivotal dog 92 if the electromagnet 98 isdeenergized.

' comprises a casing 107 mounted on the front- Excitation of the electromagnet is controlled by a suitable switch mechanism which of the machine base (see Figs. 1.and 9). Mounted on insulating sleeves 108 in opposite ends of the casing 107 are three fixed contacts 109 and. twofixed contacts-110 respectively. Two movable contacts 111 and 112 are slidably mounted on the reduced opposite ends of a reversing' piston or plunger 113 reciprocable 1n the caslng 107, and are adapted to selectively close the contacts 109 and 110 with which they constitute switches 114 and 115 respectively (see Fig. 4). A

pair of coil springs 116 on the plunger 113 tend to press thecontacts 111 and 112 outwardly against a pair ofiheads 117 on the extreme ends of said plunger.

The plunger 113 engages and is .adapted 'to be reciprocated by the downwardly extending arm ofa switch lever 118 pivotally mounted at 119 to the front of the machine base. Formed on the lower end of the lever 1184 is a wedge shaped projection 120vwhich engages either side of a pointed spring detent 121 mounted in the casing 107 to hold'the plunger 113 resiliently in oneextreme position orvthe other. The=lever118 is formed with an inclined arm which extends over thel control lever- 90, and which supports a cam roller 122 at itsiextreme end in the path of the dogs 95 and 106.

In the final movement'of the carriage 12 .to inoperative position, the cam roller 122 will ride onto a cam fa'ce 123 on the dog 106 and thereby move the plunger 113 to the right.

to close the switch 114. Upon a subsequent closure of the switch 71 by entry of the Acoarse feed gage 59 into the bore of the ork, circuits through the electromagnets respectively will be completed as follows:

from the plusmain, through wire 124, the

switch 71, and wire. 125 to the switch 114, thence branching through wire 126, the electromagnet 98, and wire 127 to the'minus and 98 main, and through Wire 128, the electro-magnet 46, and wire 129 to the minus main.

tive position, the cam roller 122 will engage an upper inclined cam face 130 on top of the dog 95,'whichwill raise the roller out of In the return movement of the carriage to operafeedof the carriage 13 and the simultaneous excitation ofthe electromagnet 98, the piv- .oted dog 92 will be tripped, thereby rendering the dog 95 ineffectual'to oscillate the lever 90, and permitting the carriage -to travel toward its inoperative position and withdraw the grinding wheel from the bore of the work. In this movement, directly after the pivotal dog 92 is positionedto the left of the right edge Aof the reversing dog 95, a sharp cam face 131 on the latter engages and depresses the cam roller 122, thereby opening the switch 114 and closing the switch 115. This results in deenergizing' the electromagnet 98, and, since the cam facie-E104y will raise the catch 102, in the release of-fthe pivotal dog 92 to operative position between the dogs 95 and 96. The dog 92 will subsequently be engaged by the dog. 96 to oscillate the lever 90 and Areverse the travel ofthe carriage 12, and will then slide along the cam face l132 again into operative position between the reversing dogs 94 and 95. The roller 122will pass under the cam 131 on the poraril j manne dog 95., and will therefore be unaffected.` The distance that the grinding wheel istemremoved from the work is determined y the position of the dog 96;

Closure of the switch 115, and subsequent closure of the switch 72 by entry of the fine feed gage 60 into the bore of the work serve to complete circuits through the electromagnets 47 and 98 as follows: from- 'the plus main, through the wire 124, the switch 72, and wire 133, then branching through the electromagnet 47- and the wire 129 to the minus mam, and through the switch 115, the wire 126, thev electromagnet 98, the wire 127 to the minus main. Thereupon the fine cross feed is discontinued, and the pivotal dog 92 is again tripped to permit movement of the carriage 12 to inoperative position. This time the dog 92 will be held in deflected position irrespective of the position of the catch 102 to permit the carriage 12 to move to its remote inoperative osi'tion. In this movement, the cam face 123 of thecam 106 raises the roller 122 to open the esA . the path of the grinding wheel 19, and is reswitch 115 and close the switch 114.

The dressing mechanism The dressing mechanism comprises a housing 135 which is mounted on the front end of. a rod 136 slidably and rotatably adjustable in a clamp sleevev137. The latter is supported by a horizontal rod 138 which is slidably and rotatably adjustable in a clamp sleeve bracket 139 secured to the rear side of the base section 25 of the headstock carriage 13. The housing 135 is formed with a bore v140-in the front end of which a bushing 141 is secured and in the rear end of which-a sleeve 142 is slidably mounted.,y Extending through the bushing 141 and into the front end of the sleeve 142 is a tool holder 143 supporting a cutting tool 144 at its front end. The rear end of the sleeve 142, which is reduced in size, extends through the rear wall of the housing 135, and is'provided with an adjusting screw 145 and lock nut 146 for adjusting the relative longitudinal position of the tool holder 143. A bolt 147 which extends through an elongated slot 148 in the housingy 135 into threaded engagement with the sleeve 142, and which engages a longitudinal notch 149 in the tool holder 143 serves to hold the parts against relative rotation. The cutting tool 144 when inoperative is located adj acent siliently held in this position by a coil spring 150 mounted between the bushing 141 and the sleeve 142.

Means is provided for projecting the cutting tool 144 into the path of the grinding wheel 19 to automatically dress the peripheral cutting surface of the latter as it is temporarily withdrawn and returned to the'work-npon completion of the coarse cross feed. This means comprises an electromagnet 151 mounted within the housing 135, and a movslidably P able cre 152 extending into the rear end of the el ctromagnet and rigidly connected to the sleeve 142 by atransverse arm 153. It will be'evident that upon excitation of .the electromagnet 151 the cutting tool 144 will be moved into operative position to dress the 'grinding wheel. 19 as the lat-ter passes by. If

at the beginning 'of the machine operation, the cutting tool 144 were rigidly mounted in line with the edge of the bore of the work blank, it could without being projected forward automatically dress the grinding wheel 19 upon withdrawal of the latter toward inoperative position to a depth corresponding to the depth of the cut on the work. In such arplace whenever the grinding wheel 19 would be withdrawn from the work past the cutting tool 144. By maintaining thecuttin tool 144 in an inoperative position during vthe actual grinding, and projecting it forward at a predetermined time, any desired depth of dressing cut can be obtained, and dressing can be confined toany desired stage of the grinding operation. Excitation of the electromagnet 151 is controlled by a switch 154 (see Fig. 3)

,comprising a pair of ixed contacts 155 and a movable contact 156. The fixed contacts are mounted on insulating bushings 157 which extend through' the lower wall of a housing 158 secured to the rear side of the machine base 10, and the movable contact 156 is mounted 4on the lower end of a stem .159 ex- 0 rangement, however, dresslng would take tending slidably through a lug 160 on the inside of the housing. The switch 154 is normally held open by a coil spring 161 mounted on'the stem 159 between a head 162 on its up- `er end and -the lug 160; Closure of the switch 154 completes a circuit through the electromagnet 151 as follows: from the plus main, through the wire 124, wire 163, the electromagnet 151, wire 164, the-switch 154, wire 165 and wire 129 to the minus main.

Rigidly mounted in the housing 158 is an electromagnet 166 which isfadapted to be excited simultaneously with the coarse feed electromagnet 46 and the electromagnet 98. Upon closure of the switches 71 and 114, a

circuit through the electromagnet 166 is completed as follows from the plus main through the wire 124, the switch 71, the wire 125, the

switchA 114, the wire 128, the electroma et 166.-, \.wire 165, andthe wire 129 to the mmus main. This circuit is broken when the roller 122 is depressed by the dog 95, and is not again completed upon closure of the switch 72. The

armature 167 having a latch 168 pivotally secured to its free end. The latch 168 continually overlies and engages the head 162 ofthe stem 159, and is formed with a hole 169 norheld above the latch by avcoil spring.17 2. A

cam 173 is adjustably mounted on the rear overhanginr side l17 of the spindle carriage 12, and is adapted to depress the pin 170 when the grinding wheel 19 is withdrawn from the work. )If the electromagnet 166 is excited, the pin 170 will engage the latch 168 to close the switch 154, and thereby actuate the cut-ting tool 144, but if the armature-is in open position, the pin will merely enter the hole 169. Slidably mounted in the projection 171 and pressed downwardly by a co1l spring 174 is a catch 175 (see Fig. 5) which upon excitation of the electromagnet 166 is adapted to lock the armature 167 in closed position, and hold it in such position after said electromagnet is deener ized. A second cam 176 formed integral w1th the right end of the cam 17 3 and positioned below the same is adapted to engage a lug 177 v on thelupper end of the catch 175 to raise the latter and release the armature 167. In movement toward the right this release will be ineffectual since the armature 167 will be mechanically held in closed position by pressure from the cam 17 3 through the pin 170 against the latch 168. In movement toward the left, however, the action of the cam 17 3 precedes that of the cam 17 6, and permits the return of the cutting tool 144 to inoperative position while the latter releases the armature 167 to position the hole 169 directly beneath the pin 170.

A modified form of the dressing mechanism is illustrated in Fig. 5, and comprises an elongated pressure llu1d cylinder 178 adjustably clamped in the sleeve 137. The cylinder is provided with spaced ports 179 and 180 which are respectively -connected by flexible tubes 181 with ports 182 and 183 in a valve casing 184 formed in the housing 158. Extending slidably through the ends of the cylinder 178 is a piston rod 185 which supports the cutting tool 144 at its front end, and a piston 186 midway of its ends. Rearward movement of the rod 185 is limited by a collar 187 thereon adapted to engage the rear end of the cylinder 17 8, and forward movement is limited by two adjustable lock nuts 188 threaded onto the rea-r end of the rod. The piston 186 throufrh'- out its reciprocation is always positioned between the ports 179 and 180. The Valve casing 184 is formed with an inlet port 189 connected by a pipe 190 into the pipe 76 leading to the main control valve 78, and with an exhaust port 191 communicating through a pipe 191l with the oil reservoir in the base 10. A reciprocable valve member 192 is mounted on the lower end of the stem 159 in the casing 158, and serves to control the flow of oil to and from the cylinder 178. When the stem 159 is depressed in a manner already described, oil will be directed through the port 180 to the rear of the piston 186 and will move the cutting tool 144 into operative position, and when the stem 159 is raised, oil will be lthe grinding wheel 19 moves past the cutting tool 144 to permit efficient dressing. Preferi ably this means takes the form of a by-pass valve comprislng a valve casing 193 secured to the rear side of the machine base 10. The

casing is formed with an oil chamber 194 con-` nected in the pipe 76 leading from the pump 74 to the main control valve 78, and with 'an exhaust port 195, opening into a pipe 196 leading to the oil reservoir. The port 195 is normally closed by a valve member 197 mounted on the lower end of a valve stem 198, the upper end of which extends slidably through a vertical extension 199 on the casing. The valve member 197 is resiliently held in closed posltion by a coil spring 200 which engages a collar 201 on the stem 198 and is confined in a bore 202 in the rojection 199 by an annular. plug 203 encircling the stem. A cam 204 adJustably mounted on the carriage 12 is adapted to depress the stem 198 to by-pass part of the oil in pipe 76 directly to the oil reservoir, thereby slowing down the speed of the carriage. The cam 204 is so positioned that in movement to the right it will engage the stem 198 just before the cam 173 engages the pin 170. f

Brief rsum of operation ltravel the left cam surface 105 raises the catch 102 to release the dog 92 if perchance they electromagnet 98 was excited, the dog 96 delects and slips over the pivotal dog '92, the dog 95 also detlects and slips over pivotal dog 92, and the dog 94 reverses the lever 90 as the grinding wheel 19 reaches the inner end of the bore in the blank A, in the order named, After feedingthe headstock carriage 13 manually to bring the work into engagement with the grinding wheel 19, the handle 57 is actuated to institute the automatic cross feed. Meanwhile the dogs 94 and 95 regularly oscillate the lever to reciprocate the grinding wheel 19 through the work. Upon each reciprocation of the spindle carriage 12, the gages 59 and 60 are withdrawn and advanced toward the work to attempt an entry into the bore.

.When the grinding operation has proceeded to the predetermined point at which the coarse feed age 59 enters the bore of the work the switch 71 closes, and through the switch 114,.which was closed through the.

' agency of the cam face 123 as the carriage 12 moved to inoperative position at the conclusionof the previous operation, completes lcircuits simultaneously through the electro-v magnets 46',' 98 and 166. The first electro-v magnet renders the coarse feed pawl 36 1x1- effectual, the second trips the pivotal'dog 92, 'and the third draws the latch 168 beneath the pin 170. The armati reof each electromagnet is automatically locked.

' In the movement of the spindle carriage 12' to the right, the dog 95 failsfto oscillate the lever 90 to reverse the travel, thereby permitting withdrawalof the grinding wheel 419 from the work. The cam faces v131 and104 `respectively engage. the roller 122 thereby breaking the switch 114 lto deenergize the three electromagnets and closing thesw'itch '115, and raise the .pin 103 to release the pivotal dog 92 into operative position between the dogs 95 and 96. The cam. 204 now de'- l presses .the stem 198, thereby opening the bypass valve to slow down the speed of the" carriage. Immediately thereafter, the cam 173 depresses the pin 170 thereby closing the cutting' tool 144 to inoperative position,

the ca'm 176 releases the armature, the cam I 204 releases the stem 198, and the dog 92 snaps into position between the dogs 94 and 95 as the grinding wheel 19 re-enters thebore of the work and reciprocates therein.

The grinding operation now continues with only the fine cross feed pawl- 37 operative, and when it is completed, the fine feed gage enters the bore of the work, thereby closing the switch 72.- This results in the excitation of the electromagnet 47 to discontinue the' cross feed, and of the electromagnet 98 to again trip the'pivotal dog 92. rIhe latter now permits movement of the lcarriage 12 to its inoperative position. In

this movement the cam face 123 engages and raises the roller 122 thereby opening the switch 115 and closing the switch 114 to place the system in condition for the next operation. The cam face 105on the right side of the dog'lO raises the pin 103 but does not thereby release the pivotal dog 92 since both switches 71 and 72 are closedn Finally the do'g 106 engages the arm 134 to automatically stop the carriage 12 in its inoperative position. Upon reloading thev chuck, the gage points 59 and 60 will be forced rearwardly to open the switchcs 1 and 72, thereby dewithout a change of feed thereafter.

energizing` the 'electromagnet 98. In movement of the carriage 12 to the left to its opera tive osition, the catch 102 willagain be raise b` the dog 106, and will release thev pivotal og 92. g.

While in the present operation, the cutting tool dresses the grinding wheel 19 between .the coarse and iinev feeds, itis to be understood-that'it can be made to dress the same during any part of the entireoperation and The machine serves to dress the grinding wheel at the most advantageous time, namely, just before' the finishing cuts of the grinding oper'- ation. The means is entirely automatic, and eiiicient and simple in operation.

We claim as our invention:

1. A grinding machine having, in combination, a rotary work holder, agrinding element, means for effecting relative movement between the two to brlng the grinding element into and out of operative grinding position with reference to the work, gage means mounted to automatically gage the work during the grinding operation, means controlled by said gage means automatically operable to lcause said first-4 mentioned means t -o remove said grinding element from said work before the completion of the lgrinding operation, and means operable upon such separation to cause said rst mentioned means to return .said element tothe Work to complete said grinding operation.

2. A grinding machine having, in combination, a carriage having a rotary workholder, a carriage havinga grinding element, means for driving said carriages relative to' each other to, reciprocate said element in engagement with the work, means for causing said first mentioned means4 to automatically discontinue said reciprocation and separate said element fromthe work, and means automatically operable upon said separation to cause said first mentioned means to return said element to the work to continue the grinding op- Aeration.

- 3. An internal grinding Amachine having, in

combination, a carriage having a workholder,

a carriage having a grinding wheel, means.

for driving said carriages relative to each other, control means for said driving means automatically operable to cause reciprocation between said work and said wheel when in operative relation and to cause a prolongation of said reciprocation in one direction at a point in the operation determined by the progress of said operation and before its completion, and means on one of said carriages nation, a rotary workholder, a grinding element, means for effecting a relative recipro- CII cation between the two while they are in continuous engagement, means automatlcally operable 'at a prmletermincd time before the completion of the grinding .operation to prolong one stroke of said reclprocation 1n one direction to etl'ect a temporary separation between said \\'orkho1dcr and said element..

5. A11 internal grinding machine having, in combination, a rotary workholdcr, a grinding element, mechanism for reciprocating the workbolder and said grinding element., one relative to the other while said element is in the bore ot' the work, and automatic means operable when the wort has been ground to a predetermined size to temporarily prolong one stroke of the reciprocating movement in one direction so as to temporarily position said element outside the bore of the work and beyond the range of working reciprocation of said element and said workholder, and to immediately return said element to the bore of the work to continue said reciprocation.

6. A grinding machine having, in combination, a rotary spindle provided with a Workholder, a grinding element, means for effecting a relative reciprocation between said holder and said grinding element, a gage mounted to perodically engage the work, vmeans controlled by saidv gagel for effecting a relative cross feed between said holder and said element-,and means controlled b said gage for temporarily suspending sai reciprocation and causing said first mentioned means to4 effeet a withdrawal from and immediate ret-urn to the work of said grinding element.

7. A grinding machine having, in combination, a carriage provided with a work-holder', a carriage provided with a grinding wheel having an operative position relative to thev work, means for etfecting a relative movement into and out of said operative position and relattive reciprocation while in said operative position between said holder and said grinding wheel to grind the work, means :for causing said first mentioned means to effect a temporary separation of said grinding wheel -and the work to bring said grinding wheel beyond the range of reciprocation before the completion vof the grinding operation, a dressing mechanism havin la cutting tool, and means controlled by sai last mentioned means operable upon said separation to project said tool into a position to be engaged by said grinding wheel.

8. A grinding machine havingin combination, a headstock carriage provided with a work holder, a grinding spindle carriage having a remote inoperative position and an operative position and provided with a grinding element, means for effecting a relative cross feed between saidk carriages, means for moving said grinding spindle carriage from. its remote lnoperative position to its operative position, and reciprocating it therein, andl means controlled by the'progress of said cross feed to cause said last mentioned means to effect a temporary separation of said grinding clcment'and the work during the Grinding operation and to effect a return of sald grinding spindle carriage into inoperative position at the completion of the grinding opera-l tion.

9. In a grinding machine having a headstock carriage provided with a workholder, a grinding spindle carriage provided ,with a grinding element and having a remote inoperative position and an operative position relatlve to said workholder, means for recipro-v dressing mechanism having in combination,

a dressing tool movably mounted at one side of said workholder, and means for projecting said tool into the path of said grinding element in position to ldress the cutting surface of the latter at said separation, said last mentioned means being controlled by said second mentioned means to act substantially simultaneously with the initiation of said prolongation.

10. In a grinding machine, a grinding wheel having a reciprocatory working traverse'relative to the work, means for automatically procuring an amplified traverse of said wheel when the work, by grinding, has reached a predetermined size, means for automatically disposing awheel dressing device in the amplified path of movement of sa'd wheel, and means for automatically returning said wheel to its normal working traverse on the return stroke of said amplilied traverse.

11. In' a grinding machine, a grinding wheel,-means operable in the grinding of each work-piece for automatically procuring two successive withdrawals of said wheel from sald work, and automatic means for subjecting said wheel to a dressing and truing opera-y tion on the first withdrawal, and for avoiding the dressing of said wheel on the second withdrawal.

12. In a grinding machine, a grinding wheel, means operable in the grinding of each workpiece by said wheel forV automatically procuring two successive withdrawals of said wheel from the work, each withdrawal carrying said wheel through a wheel dressing position, a wheel dressing device automatically made operable on said wheel during said first withdrawah and means for automatically preventing the operation of said device onthe second withdrawal.

13. In a grinding machine, a grinding wheel, means operable in the grinding of each workpiece by said wheel for automatically procuring two' successive passages of said wheel through a wheel dressing position, a.

grinding wheel dresser, means for disposing said dresser in operative position oii said first passage aiid means for maintaining said. dresser in inoperative position on said second passage.

14. In .a grinding machine, a grinding -wheel, a wheel ,dressing device, a work calipering device,the latter adapted to make a contact at an intermediate stage in the inding operation to omplete an electrical circuit, means dependent uponand set in operation by the completion of said circuit for automatically subjecting said grinding wheel to the action of said dressing device, and means, then acting to break said electrical circuit, thereby to avoid a second dressing operation on said wheel during grinding of t e same workpiece, notwithstandingv maintenance of the contact made by said calipering device.

15. In a grinding machine, a grinding wheel, a wheel dressing device,means operable automatically at an intermediate stage in the grinding of each workpiece to complete an electrical circuit by making a contact, means dependent upon and set in operation by the completion of said circuit for automatically subjecting said grinding wheel to the action of said dressing device, and means, automatically then acting to break said circuit independently of the contact that completed the same, thereby to avoid a second dressing operation on said wheel during grinding of the saine workpiece through the maintenance of said contact.

16. In a grinding machine, a grinding wheel, a wheel dressing device, an electromagnet adapted, when energized, to effect movement of said device into dressing position, a second electromagnet adapted, when energized., to effect movement of said grinding wheel through said dressing position, and means, responsive to the energization of one of said electromagnets, for completing an electrical circuit through the other of said electromagnets.

17. In a grinding machine, the combination with a grinding wheel, of means for causinga relative reciprocatory grinding motion between said wheel and the work, including means for causing a final cessation of said grinding by separation of work and wheel, a dressing tool disposed normally in inoperative relation to said wheel, a work calipering mechanism, means operable by said caliper- 'ing mechanism, before and in advance of said final cessation of the grinding, for moving said'dressing tool into operative position w-ith respect to saidwheel, so as to dress the grinding surface of the latter,and means for thereafter disposing said dressing tool in its inoperative position, thereby avoiding engagement of the same with said wheel, upon the separation of wheel and work at the cessation of grinding.

18.` In an internal ginder abrading means, work holding means, means operable to separate the work holding means from the abrading means, a feelin finger engaging the inner surface of the work for causing operation of the separating means when the work is finished to separate, and return the work holding means and the abrading means to operative relation, substantially as set forth.

19. In a grinding machine, means for normally effecting relative reciprocation between the grinder and the work without separation of one from the other, means for automatically etfecting separation between grinder and work, a dressing device a plicable to dress said grinder during sai separation, and means for automatically restoring the unseparated normal relative reciprocation between grinder and workar- 20. In a Grinding machine, means for nor-` traverse between said wheel and the work, a-

grinding wheel dressing device inoperative on said wheel during said working traverse, means set in operation by said work calipering d evice for automatically rendering said dressing device operative on said wheel, and means for automatically eii'ecting resumption of said relative working traverse, after the dressing operation.

22. In a grindin machine, a grinding wheel, means for e ecting a relative Working traverse between said grinding wheel and a workpiece, means automatically operable to separate said grinding wheel and said workpiece, means for automatically subjecting said grinding wheel to a dressing operation 'during said separation, and means for automatically effecting a resumption of said relative working traverse after said dressing operation.

23. In a grinding machine, a grinding wheel, awheel dressing device, a work calipering device, means set in operation by said calipering device for procuring an interruption of the grinding operation, and for subjecting said wheel to said dressing device during said interruption, and for automatically procuring resumption of the grinding operation on a workpiece after said dressing operation.

24. A grinding machine having, in combination, a rotary work holder, a grinding element having an operative position in which it is. adapted to grind the work, means for effecting a relative movement between the two mounted to automatically gage the work, a

. v 26. In a grinding machine, a grinding dressing mechanism having a cutting tool, and means controlled by said gage for controlling sai'd first vmentioned means to withdraw'said grinding element out of operative relation. t'o the work, it then moving relative to the. cutting tool of saiddiessing mechanism, and said means then returning it to operative position relative to the work. 0 0

25. In a grinding machine, a grinding wheel having a reeiprocatory working traverse relative to the work, a work calipering device, a wheel ldressing device, means set in operation by said calipering device when the work reaches a predetermined size for automatically increasing vthe traverse of said wheel, thereby to subject it to the actionof said dressing device, and means responsive to said increased traverse for limiting the latter to a single reciprocation of said wheel.

wheel having a reciproeatory working traverse relative to the work, a grinding wheel dresser, a work caliperingdevice, means set in operation by said work calipering-device for increasing the traverse bet-Ween said wheel and the work in one direction, thereby to subject said wheel .to the action of said dresser, and means, responsive to said increased traverse, for automatically restoring the normal working traverse between said wheel andthe work.

27. In a grinding machine, a grinding wheel'having' a reciprocatory working traverse relative tothe work, means operable at an intermediate point in the grinding of each workpiece for amplifying said traverse to carry said wheel through a wheel dressing position, a grinding wheel dresser for operating on said wheel in its passage through said dressing position, and automatic means for avoiding the dressing of said wheel by said dresser on the subsequent passage of said wheel through the dressing position at the conclusion of the grinding of the same workpiece.

28. In a grinding machine, means for-effecting a.relative working traverse between the grinding wheel and the work, means operable automatically before the completion of the grinding operations, to amplify said traverse, a dressing device applicable to dress the said wheel, at this stage, and means for automatically resuming'said working traverse after said dressing for the final and finishing cuts of the grinding wheel to bring said work to size.

29. lIn a grinding machine, a grinding wheel, a work calipering device, means for procuring a relativereeiprocatory Working traverse between said wheel and the work, a wheel dressing device disposed beyondl the path of vsaid relative reciprocatory working traverse, means set in operation by said work calipering device in advance of the final and finishing cuts taken on each piece of work by said wheel, for automatically amplifying said traverse, thereby to include said dressing device in the path of -said wheel, and means for automatically resuming said working traverse, for the final and finishing cuts of the grinding wheel to bring said work to size.

30. In a grinding machine, a grinding wheel having a recipi'ocatory working traverse relative to the work, means for automatically procuring an amplified traverse of said wheelf when the work, by-- grindinv, has reached a predetermined size, means or automatically disposing a wheel dressing device in t-he path of said wheel on said amplified z traverse thereof, and means for automati-A cally resuming the normal recipiocatory working traverse between grinding wheel and work to bring the latter to the desired finished size.

31. A grinding machine having means for effecting a relative working traverse between its grinding wheel and a workpiece, said traverse being substantially coextensive in length with said workpiece, a wheel dressing device J beyond the range of said normal working traverse, means automatically operable at an intermediate stage in the grinding operation on each workpiece for separating said grinding wheel and said workpiece, to subject said wheel to the action of 'said ldressing device,

and means for automatically restoring said normal working traverse between wheel and workpiece forthe final and nishing cuts req'uired to bring each workpiece to the desired size.

32. The combination witha grinding instrumentality, and means for causing a relative motion between it; and the work, including means for ycausing a final cessation of said motion, and a dressing tool, of work engaging calipering mechanism, the position of which changes as the work is ground away,

and mechanism operated by such change of position before and in advance of the said final cessation of the grinding motion, for causing an engagement between said dressing tool and grinding instrumentality such as to dress the grinding surface of the latter andl then to automatically separate said dressing tool and grinding instrumentality.

33. In a grinding machine, a grinding wheel, a work calipering device,` a wheel dressing device, and means successively set in operation by said calipering device, in the grinding of each workpiece, for effecting two separations between the grinding wheel and the workpiece, the first subjecting said wheel to said dressing device, and the second procuring cessation of the grinding operation.

34. In a grinding machine, a,v grinding wheel, a wheel dressing device, and means responsive to the progressive change in size of each workpiece, during the grinding by l said whee1,'.for ei'ecting successive separaholder and a t-rulng tool mounted on saidl support, means for causing relative traverse between the grlnder and sa1d support, lncluding means permitting altering the extent of` said traverse between two ranges, one of which carries the parts through operative traverse between the grinder and work holder alone, and the other of which carries the parts through operative traverse bet-Ween the grinder and both the work holder and truing tool, a work sizing mechanism, means brought into action when said work sizing mechanism assumes a predetermined position for altering the said traverse from the shorter to the longer range, means automatically causing resumption of said shorter range, and means preventing immediate subsequent resumption of the longer range despite the assumption by said sizing mechanism of said predetermined position.

36. A grinding machine having, in combination, a support having a rotary work.

holder, a support having a grinding element means for moving said supports relative to each other to reciprocate said element in engagement with the work, means for causing said first mentioned means to automatically discontinue said reciprocation and separate said element from the work, and means automatically operable upon said separation to cause said first mentioned means to return said element to the work to continue the grinding operation.

37. A grinding machine having, in combination, a headstock provided with a work hold-cr, a grinding spindle carriage having a remote inoperative osition and an operative position and provided with a grinding element, means for effecting a relative cross feed between said carriage and said headstock, means for moving said carriage from its remote inoperative position to its operative position, and reciprocating it therein, and means controlled by thev progress of said cross feed to'cause said last mentioned means to eiiect a temporary separation of said grinding element and the work during the grinding operation and to effect a return of said carriage into inoperative posit-ion at the completion of the grinding operation.

38. A grinding machine having, in combination, a work holder, a grinding wheel, a

carriage supportingand carrying one of said parts, means for moving said carriage to effect a relative movement of said grinding wheel into and out of operative position relative to the work and for efecting a relative reciprocation of said grinding Wheel and said work while they are in operative relation in order to grind the work, means for causing said Iirst mentioned means to effect a temporary separation of said grinding Wheel and the work to bring said grinding wheel beyond th-q range of reciprocation before the completion lof the grinding operation, a dressing mechanism having a cutting tool, and means vcontrolled by said last mentioned means operable upon said separation to project said tool into a position to be engaged by said grinding wheel.

39. In a grinding machine having a headstock provided' with a Work holder, a grinding spindle carriage provided with a grinding element and having a remote inoperative position and an operative posit-ion relative to said work holder, means for reciprocating said carriage in said operative position, and means for effecting a temporary prolongation of said reciprocation in one direction to separate said work holder and said grinding element at a predetermined point in the grinding operation, a dressing mechanism having in combination, a dressing tool movably .mounted at one side of said work holder and means for projecting said tool into the path of said grinding element in position to dress the cutting surface of the latter at said separation, said last mentioned means being controlled by said second mentioned means to act substantiall simultaneously with 'the initiation of sai prolongation.

40. An internal grinding machine having, in combination, a support having a work holder, a support having a grinding wheel', means for driving -said supports relative to each other, control means for said driving .means automatically operable to cause reciprocation between said work and said wheel when in operative relation and to cause a prolongation of said reciprocation in one direction at a point in the operation .determined by the progress of said operation, and before its completion, and means on one of said supports automatically operable through said separation to eii'ect through said driving means an immediate return of the work and said wheel into operative relation..

4l. In a grinding machine, means for causing relative reciprocation between work holding means and a grinding wheel, a wheel dressing device, means for pro'ecting the wheel dressing device up to the ine of the said reciprocation, simultaneously operated means for causing the said reciprocation to include the wheel dressing device in its path, and a control adapted to cause the speed of reciprocation when said dressing device is inthen to automatically restore the relative moeluded to be dierent from the speed of reciprocation when said dressing device is v.not in the said path.

42. In a grinding machine, the combination with a table, means to reciprocate said table, a dressing tool, and means to move said dressing tool into an operative position, of means actuated simultaneously with the movement of said dressing tool into operative position to control said mea-ns to reciprocate the table whereby to reciprocate it at reduced speed.

43. A grinding machine comprising in combination a grinder, a support, a work holder and a truing tool mounted on said support, means for causing relative traverse between the grinder and said support including means permitting altering the extent of said vtraverse between two ranges, one of which carries the parts through operative traverse between the grinder and work holder alone and the other of which carries the parts through operative traverse between the grinder and both the work holder and truing tool, means permitting varying the speed of said traverse, and a device operable to make both of said'two last mentioned means eiec- 47. In a grinding machine, a grinding Wheel, a work caliperlng device,a wheel dressing device disposed normally out of the path `of said grinding wheel, means set in operation by the movement of said work caliper-ing device to a predetermined polnt for disposing said dressing device in the path of-said wheel, and mea-ns for preventing a second disposal of said dressing device in said path during the subsequent grinding ofthe same piece of work.

48. In a grinding machine, a grinding wheel, a work calipering device, an electrical contact made by said device at an intermediate point in the grinding of each workpiece, for effecting the movement of said wheel through a wheel dressing position, and means, responsive to the return movement of said wheel, for. preventing a second movement to wheel dressing position during the grinding ofthe same workpiece, notwithstanding the maintenance of said electrical contact.

In testimony whereof-we have hereunto affixed our signatures.

HERBERT E. KEMPTON. KEITH F. GALLIMORE.

ing relative traverse between the grinder and Work while the grinder is operating on the work, means for extending the traverse to include the wheel dressing point in the path of reciprocation so that the wheel may be dressed, including means for causing resump- 'tion of the aforesaid relative traverse between the grinder and the work, and a control adapted to cause the speed of reciprocation while the grinder is operating on the work prior to and subsequent to the dressing operation to be y'different from the speed of'reciprocation while the grinder is being dressed.

45. The combination with a grinding instrumentality, and means for causing a relative motion between it and the work, including means for causing a nal cessation of said motion, and a dressing tool, of work engaging calipering mechanism, the position of which changes as the work is ground away, and mechanism operated by such change of position before and in advance of the said causing an engagement between said dressing tool and grinding instrumentality such asv to dress the grinding surface of the latter and said dressing point into the path of the grinding wheel, and electromagnetic means for setting said means in operation. 

